Preheat oven to 350°.
Lightly spoon flour into dry measuring cups, and level with a knife. Combine flour and the next 6 ingredients (through salt) in a large bowl, stirring with a whisk.
Combine sour cream, butter, and egg, stirring with a whisk. Add egg mixture to flour mixture; stir to form a soft dough. Turn dough out onto a lightly floured surface; knead lightly 7 or 8 times.
Divide dough in half. Place 1 dough portion on each of 2 baking sheets coated with cooking spray and sprinkled with 1 1/2 tablespoons cornmeal; turn to coat top of dough. Roll each portion into a 12 x 8-inch rectangle (about 1/8 inch thick). Bake at 350° for 15 minutes or until browned and crisp. Remove from pan, and cool completely on wire racks. Break into 24 crackers.